=> Grub 2 is installed in the MBR of /dev/sda and looks on the same drive in
partition #256 for /boot/grub.
=> Grub 2 is installed in the MBR of /dev/sdb and looks on the same drive in
partition #256 for /boot/grub.
=> Grub 2 is installed in the MBR of /dev/sdc and looks on the same drive in
partition #256 for /boot/grub.
=> Grub 2 is installed in the MBR of /dev/sdd and looks on the same drive in
partition #256 for /boot/grub.
=> Grub 2 is installed in the MBR of /dev/mapper/nvidia_fdcjiejd and looks on
the same drive in partition #256 for /boot/grub.

### BEGIN /etc/grub.d/30_os-prober ###
if [ ${timeout} != -1 ]; then
if keystatus; then
if keystatus --shift; then
set timeout=-1
else
set timeout=0
fi
else
if sleep --interruptible 3 ; then
set timeout=0
fi
fi
fi
### END /etc/grub.d/30_os-prober ###

### BEGIN /etc/grub.d/40_custom ###
# This file provides an easy way to add custom menu entries. Simply type the
# menu entries you want to add after this comment. Be careful not to change
# the 'exec tail' line above.
### END /etc/grub.d/40_custom ###

This thread can be closed.
I found a solution for my problem.
The alternate installer now can also setup complex RAID configurations including RAID10, so I erased my manual attempt and did it entirely with the installer.